Hematology, Serum Electrolytes and Renal Biopsy

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Hematology, Serum Electrolytes and Renal Biopsy

• Stephen P. DiBartola, DVM
• Department of Veterinary Clinical Sciences
• College of Veterinary Medicine
• Ohio State University
• Columbus, OH 43210

The Nephronauts
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Red blood cells

• Nonregenerative anemia in chronic renal failure
• Effect of dehydration on PCV and TPP
• Polycythemia

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White Blood Cells

• Stress of chronic disease may cause lymphopenia
  in chronic renal failure

Platelets

• Platelet dysfunction despite normal numbers may
  occur in uremia

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Electrolytes

• ECF electrolytes
• Sodium
• Chloride
• Bicarbonate
• ICF electrolytes
• Potassium
• Phosphorus

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Sodium

• Dog 145 (140-155) mEq/L
• Cat 156 (149-162) mEq/L
• Horse 139 (132-146) mEq/L
• Cattle 142 (132-152) mEq/L

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Serum sodium concentration

• Serum sodium concentration is an indication of
  the amount of sodium RELATIVE to the amount of
  water in ECF and provides no direct information
  about total body sodium content

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Serum sodium concentration

• Hypernatremia means hyperosmolality
• Hyponatremia usually means hypoosmolality

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Hypernatremia

• Pure water loss
• Hypotonic fluid loss
• Gastrointestinal
• Third space
• Renal
• Gain of impermeant solute

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Hyponatremia

• With hypervolemia
• Severe liver disease, congestive heart failure,
  nephrotic syndrome
• With normovolemia
• Psychogenic polydipsia, anti-diuretic drugs,
  hypotonic fluids
• With hypovolemia
• GI loss, third space loss, hypoadrenocorticism,
  diuretics

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Chloride

• Dog 110 (105-115) mEq/L
• Cat 120 (115-125) mEq/L
• Horse 104 (99-109) mEq/L
• Cattle 104 (97-111) mEq/L

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Serum chloride concentration

• Cl- and HCO3- are the main resorbable anions in
  renal tubular fluid and abnormalities in one
  often result in abnormalities of the other
• Normal ratio of Na to Cl- in ECF is 1.3 to 1 and
  gain or loss of equal amounts of Na and Cl- will
  disturb this relationship. Only a gain or loss of
  4 Na for every 3 Cl- would preserve this
  relationship

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Hyperchloremia

• Excessive loss of Na relative to Cl- (e.g.
  diarrhea)
• Excessive gain of Cl- relative to Na (e.g.
  NH4Cl, 0.9 NaCl, hypertonic NaCl, salt
  poisoning)
• Excessive Cl- retention by kidneys (e.g.
  compensation for chronic respiratory alkalosis)

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Hypochloremia

• Vomiting of stomach contents or sequestration of
  fluid in stomach
• Diuretics (e.g. furosemide)
• Compensation for chronic respiratory acidosis

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Potassium

• Dog 4.5 (3.5-5.5) mEq/L
• Cat 4.5 (3.5-5.5) mEq/L
• Horse 3.8 (2.6-5.0) mEq/L
• Cattle 4.8 (3.9-5.8) mEq/L

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Potassium Balance
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Translocation of potassium
ICF
ECF
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Hyperkalemia

• Increased intake (alone usually not sufficient to
  cause hyperkalemia if renal function adequate
  unless iatrogenic)
• Translocation (ICF to ECF)
• Acute mineral acidosis, insulin deficiency
• Decreased renal excretion
• Urethral obstruction, uroabdomen, oligoanuric
  renal failure, hypoadrenocorticism, some drugs

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Hypokalemia

• Decreased intake (alone not usually sufficient to
  cause hypokalemia)
• Translocation (ECF to ICF)
• Alkalemia, insulin and glucose
• Increased loss
• GI, renal

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Total CO2 or bicarbonate

• Dog 21 (17-24) mEq/L
• Cat 20 (17-24) mEq/L
• Horse 27 (24-30) mEq/L
• Cattle 25 (20-30) mEq/L

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Total CO2

• Anaerobically measured, this includes HCO3-,
  dissolved CO2 and negligible amounts of
  carbamino-CO2, H2CO3, and CO3-2
• Aerobically measured, it is essentially
  equivalent to HCO3-

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Total CO2

• Determination of total CO2 alone does not allow
  complete characterization of acid base
  disturbances
• High total CO2 usually means metabolic alkalosis
  but compensation for respiratory acidosis could
  contribute
• Low total CO2 usually means metabolic acidosis
  but compensation for respiratory alkalosis could
  contribute

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Serum total calcium concentration

• Dog 10.1 (9.0-11.3) mg/dL
• Cat 9.2 (8.0-10.5) mg/dL
• Horse 12.4 (11.2-13.6) mg/dL
• Cattle 11.0 (9.7-12.4) mg/dL

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Components of serum total calcium concentration
Ionized Calcium (50)
Complexed Calcium (10)
Protein-bound Calcium (40)
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Normal serum calcium concentrations in dogs

• Total 9 to 11 mg/dl
• Ionized 5.1 to 5.7 mg/dl

Routine serum biochemical profile returns serum
total calcium concentration
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Effect of acid base balance on serum calcium
concentration

• Acidosis tends to increase the ionized fraction
  and decrease the protein-bound fraction
• Alkalosis tends to decrease the ionized fraction
  and increase the protein-bound fraction

These results are due to the effects of acid base
balance on the net charge of plasma proteins
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Effect of hypoalbuminemia on serum calcium
concentration
Ionized Calcium (mg/dL)
Complexed Calcium (mg/dL)
Protein-bound Calcium (mg/dL)
2
Normal
Hypoalbuminemia
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Correction of hypocalcemia for hypoalbuminemia

• Corrected Calcium Calcium Albumin 3.5
• Works reasonably well in dogs
• Unreliable in cats

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Hypercalcemia in chronic renal failure (example)
Ionized Calcium (mg/dL)
5
Complexed Calcium (mg/dL)
1
4
Protein-bound Calcium (mg/dL)
CRF
Normal
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Hypercalcemia

• Dehydration
• Various malignancies
• Hypoadrenocorticism
• Renal failure
• Hypervitaminosis D
• Primary hyperparathyroidism

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Hypercalcemia in horses with renal failure

• May be related to fact that horses normally
  absorb large amounts of calcium from their GI
  tract and rely on their kidneys to excrete it
  (calcium carbonate crystals are common in horse
  urine)

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Hypocalcemia

• Hypoalbuminemia
• Renal failure
• Ethylene glycol poisoning
• Eclampsia
• Acute pancreatitis
• Primary hypoparathyroidism

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Phosphorus

• Dog 4.2 (2.5-6.0) mg/dL
• Cat 6.3 (4.5-8.1) mg/dL
• Horse 4.3 (3.1-5.6) mg/dL
• Cattle 6.0 (5.6-6.5) mg/dL

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Serum phosphorus

• Largely a mixture of H2PO4- and HPO4-2
• The net valence and number of mEq of phosphorus
  in ECF are influenced by pH hence it is easier to
  talk about phosphorus in terms of mMol or mg of
  elemental phosphorus

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Hyperphosphatemia

• Translocation (ICF to ECF)
• Decreased renal excretion
• Increased intake
• Young growing animal

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Hypophosphatemia

• Translocation (ECF to ICF)
• Decreased renal reabsorption
• Decreased intestinal absorption

Hypophosphatemia may occur in some horses with
renal failure
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Renal Biopsy Indications

• Differentiation of renal diseases that may differ
  in their prognosis
• Differentiation of ARF from CRF
• Determination of status of basement membranes in
  ARF
• Determination of response to therapy
• Determination of progression of disease

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Renal Biopsy Contraindications

• Coagulopathy
• Severe hydronephrosis or perinephric pseudocyst
• Renal or perirenal abscess
• Pyonephrosis
• Solitary kidney
• Pyelonephritis
• Renal neoplasia
• Extremely small kidneys

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Renal biopsy General considerations

• Adequate patient evaluation
• Choice of technique
• Choice of biopsy instrument
• Direction of instrument into kidney
• Hemostasis
• Anesthesia

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Pre-biopsy evaluation

• Coagulation ability (role of buccal mucosal
  bleeding time)
• IV catheter and fluid administration
• PCV TPP after fluids but before biopsy
• Fluid diuresis

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Methods of renal biopsy

• Open surgical
• True percutaneous
• Keyhole
• Laparoscopy
• Ultrasound-guided (currently in use at OSU VTH)
• Needle aspirate NOT a biopsy!

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Renal biopsy Keyhole technique
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Renal biopsy Ultrasound-guided
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Post-biopsy evaluation

• Fluid diuresis for 12 hours
• Monitor PCV TPP at appropriate intervals over
  12 to 24 hours

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Renal biopsy Complications
Microscopic hematuria vs macroscopic hematuria
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Renal biopsy Complications

• Hemorrhage
• Infarction
• Hydronephrosis
• Other extremely rare (e.g. infection, retention
  cyst, AV fistula, urine fistula)

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Handling the biopsy

• Avoid touching the biopsy specimen at all
• Preservation of specimen
• 10 buffered formalin for routine light
  microscopy and peroxidase-immunoperoxidase
  immunopathology
• Michels medium for direct immunofluoresence
• 2 glutaraldehyde for transmission electron
  microscopy